The invention relates to a tunnel finisher.
A tunnel finisher is known from DE-PS No. 35 19 568. This known tunnel finisher has pneumatic rollers provided with a coat in the form of a cylindrical envelope. The cylindrical envelope consists of a fabric hose or of a sheet material sewed together substantially to the shape of a hose, and is secured to the discs by means of annular springs received in annular grooves of the top and bottom discs. In order to enable such a closed cylindrical envelope to be replaced, the shaft is divisible between the two discs. To this purpose each disc carries a stub shaft directed towards the other disc, the two stub shafts being adapted to be interconnected by means of a tubular member. For replacing the envelope, one of the annular springs is released, permitting the envelope to be shifted to a position for giving access to the tubular member. The threaded connections between the tubular member and the two stub shafts are then released, so that the tubular member can be slipped completely onto one of the stub shafts. This exposes the free end of the other stub shaft, so that the envelope can be pulled out through the thus formed gap after the second annular spring has been released. This procedure is obviously rather complicated, because it requires the cylindrical envelope to be compressed to a reduced length for giving access to the threaded shaft connections. This process is additionally complicated by the fact that the replacement of the envelope has to be carried out in the known tunnel finishers with the pneumatic rollers mounted in position, some of these positions within the tunnel finisher being rather difficult to gain access to. It is also difficult to keep the tubular shaft member in the raised position for dividing the shaft and at the same time to remove the envelope. Similar difficulties are encountered when mounting a new envelope.
It is also known to provide the envelopes of tunnel finishers with zip fasteners for at least marginally facilitating the replacement of the envelopes within the tunnel finisher. The zip fasteners employed for this purpose are rather expensive, however. In addition it is scarcely avoidable that a moisture condensate is formed on the metal parts of the zip fasteners.